1. Field of the Invention
The present invention relates to a semiconductor device, such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) having a dual-gate electrode, and a method for fabricating the semiconductor device.
2. Description of the Related Art
With reference FIG. 6, a MOSFET having a dual-gate electrode will be described as a conventional semiconductor device. FIG. 6 is a cross-sectional view illustrating a boundary portion between an n-type MOS region and a p-type MOS region in the conventional MOSFET. As shown in FIG. 6, the conventional MOSFET includes an isolation region 102 formed in a silicon substrate 101; a p-type well region 103 acting as an n-type MOS region and an n-type well region 104 acting as a p-type MOS region, each surrounded by the isolation region 102; a gate oxide film 105 formed over the silicon substrate 101; a dual gate electrode composed of an n-type polysilicon electrode 109A and a p-type polysilicon electrode 109B formed on the gate oxide film 105; and a metal silicide film 112 formed on the n-type polysilicon electrode 109A and the p-type polysilicon electrode 109B. The n-type polysilicon electrode 109A and the p-type polysilicon electrode 109B are formed by forming a polysilicon film on the gate oxide film 105 and then introducing an n-type impurity, such as phosphorus (P), in the n-type MOS region and a p-type impurity, such as boron (B), in the p-type MOS region, respectively.